This invention relates to cooking ovens. In particular, it relates to ovens for forced convection cooking with superheated steam, saturated steam, or heated air.
The art of cooking an object in an oven involves raising the core temperature of the object to a desired value while controlling the temperature and other conditions on the outside of the object to achieve a desired surface appearance. When two or more objects are placed in an oven to be cooked, an additional problem arises. That is the problem of maintaining uniformity among objects that are cooked. As time passes in the cooking cycle of a particular object, it is necessary to arrange some kind of circulation of heat to prevent stratification in the oven that might lead to uneven cooking of different objects or of different regions of the same object.
One oven function that is sometimes used to assist in cooking is to circulate steam with or in place of the hot air in the oven. The steam is produced by a boiler that typically is located outside the oven. Water is piped into the boiler and is heated by a local unit to generate steam that is conveyed into the oven for circulation. While it is common to specify a maximum level of dissolved solids in the water to be used in such a boiler, a level that normally requires softened water, it still is necessary to clean the boiler periodically to remove deposited minerals from the water as well as removing any contaminants from cooking.
Many ovens that circulate steam to cook can also be operated as steamers, holding or circulating saturated steam to thaw frozen foods, cook vegetables, or maintain cooked foods hot and ready to serve. Such a use of the oven produces condensate which must be removed from the oven without interfering with the cooking or steaming function.
Another problem in the operation of cooking ovens is that of temperature control. It is desirable to have the temperature uniform in space throughout the oven, and uniform as a function of time after the oven has come up to a particular temperature. It is not uncommon for the control range of the temperatures in both commercial and residential ovens to vary as much as 50.degree. F. in both space and time. Variations in space can be minimized by circulating air with a blower or the like and by designing the interior of the oven to minimize the blockage of flow by pans and other containers of foods to be cooked. Variations of temperature with time are functions of temperature sensors and controllers that are used in response to them.
A further problem in cooking arises from the fact that cooking cycles sometimes require temperature changes. In such a case, it is necessary to have some means of storing a desired temperature control level for a particular time and a different temperature control level for a different period of time. Information such as this is best handled by a microprocessor with associated memories.
A complete kitchen, industrial or residential, may call for the processing of dough for bread or pastries. This includes the function known as proofing, which is the holding of dough at a controlled temperature and possibly also at a controlled humidity to enable yeast to work and raise the dough. The control of both temperature and humidity enables an oven to be used as a proofing oven.
In kitchens, industrial or residential, it is often desirable to cook overnight and hold cooked items ready to be used on a following day. This normally calls for a relatively high cooking temperature for a predetermined time, followed by holding at a lower temperature. It is often convenient when holding at the lower temperature to be able to control the humidity to prevent excessive drying of cooked items during the holding period.